右肩の蝶
by Chocolatey Sheep
Summary: Based off Migikata no Chou/Butterfly on your Right Shoulder(obviously). NONCEST; Rated T for occasional language and future dark(ish) themes.
1. Chapter 1

**A/N: Hi! Thanks for clicking on this fanfic! :3**

 **I only have a rough idea of the plot, so any criticism would be appreciated!**

 **Rin and Len have just turned 16; Miku and Luka are 17; everyone else mentioned is also 16. Rin's birthday is pushed one day late(28 Dec).**

 **Outfits mentioned are from Adolescence.**

 **DISCLAIMER: I don't own Vocaloid... but someday...**

* * *

Rin ran her fingers through her short blonde hair, worried aquamarine eyes gazing back at her in the mirror. She just couldn't get the angle of her bow right. "Stop fussing!" her sister Miku'd said. Easy for her to say. She wasn't the one who would have her beloved over for her birthday party, which would be only one hour away…

It was really rather odd, if you thought about it. Len Kagamine, best friend and (unknown to him) Rin's very first love, was eerily similar to her. Same sun-streaked golden hair that fell just below the shoulder, same clear blue eyes that were a mere shade different; Len's, tinted dark violet; Rin's, just a little too green. Len was no less than an inch taller than Rin, though Len was really only a day older. People would often mistake them for siblings or even twins, and even Miku had once said that they looked like each other's mirror image, albeit genderbent.

But that was besides the point. Rin sighed, dragging the white ribbon out of her yellow tresses. She'd just have to go without it today, she decided. Her outfit would have looked better with the black, anyway, but she'd misplaced it sometime during the last few days, and couldn't borrow Miku's since she'd been planning to use them herself. _At least that looks like that's one problem that's literally out of my hair_ , she mused with a sarcastic smile.

She ran her fingers through said hair in an attempt to straighten it and inserted her clips into her bangs to secure them in to place, then straightened her dress, smiling a little when she remembered that Len would be in a matching outfit. Whereas Rin was wearing a white dress with spaghetti straps that were tied around her neck and two rows of ruffles down the front, Len would be in a vest and yellow tie, bartender style. Rin had wanted a jazzy party, after all. She snickered when at the memory of Len's appalled face when they told him about the dress code, yet surprisingly he'd protested little. Although it was probably just a sign of true friendship, Rin liked to think it was because he wanted to impress her.

Rin straightened and smiled into the mirror again, this time nervously, trying to calm her irregular heatbeat. Slowly, her smile grew more determined. _You may not look at me now, Len,_ she thought, _but one day, you'll see!_

 _Just you_ wait _and see!_

* * *

Rin slumped against her bedroom wall and let out yet another of her incessant sighs. Oh, she'd waited, alright.

Fat lot of good _that_ did her.

It was hard to believe, much less remember, that she was so happy and still cared so much about what Len thought of her just a few days ago. After all, what was the point? All the same, Rin couldn't help but replay and replay the memory in her mind, at once envying and hating the girl those days ago both. She was so naive, so blissfully ignorant. Part of Rin wanted only to protect that happiness.

The other part wanted to slap her, because he'd never cared anyway. But that wasn't even the worst part, because Rin still cared.

Rin still cared, even if Len didn't. And she cared far more than she would've liked and far more than she should have.

The worst part was that she knew she would never stop caring.

Just what had happened, anyway?

 _Just what had happened to that girl a few days ago?_

* * *

That girl, a few days ago, was restlessly fidgeting on the couch, too agitated to do the one thing that might have soothed her nerves and eat an orange. With eyes resolutely fixed on the clock, as if wanting time to go faster and let the doorbell ring, suddenly ring it did.

Rin leapt up and thrust the door open, despite the fact that the person at the other side of the door was not, in fact, Len.

"Oh hi, Luka," Rin chirped, pushing down her disappointment. She plastered a delighted smile on her face and steered Luka in. Where the hell was Len? She bit her lip; It was 3:56 PM. She shook her head quickly; If Len was wasn't here yet, that would be his problem.

Yet she couldn't help but worry about it as more and more time passed. It wasn't unlike Len to not be early, but it was even more unlike him to be late. Even IA had arrived, and she was late to pretty much everything. Then again, so was Neru due to her phone addiction, and she was the only person left now who hadn't arrived other than Len.

Finally- finally- the bell rang again, and Rin sprang toward it, not caring if it wasn't Len, not caring that it was 4:22 and he was precisely 22 minutes and 18 seconds late, because time was just a number-

When Rin looked back later, she would think of it was the precise moment the world fell away.

"Hi, Len, Neru! That's great, both of you arrived, now everyone's here," Rin sang, smiling at both of them. "Why so late, though?"

Then she saw their linked hands.

Rin's breath jammed violently in her throat.

"Oh, that..." Len said hesitantly, as he took off his coat.

Len, who was not in his bartender outfit.

 _Am I dreaming?_ _I'm having a nightmare, wake me up, hurry._

"The thing is, Neru wanted to, uh, ask me something," he said. "And I'm not dressed up, cause Neru wanted to borrow the costume for a while. That's fine, right?"

 _No, of course it's not alright! They were supposed to be matching outfits! They weren't supposed to be worn by anyone else!_

"Yeah, sure," Rin heard herself saying distantly. "Of course. Why don't you go get some bananas? I saved some for you."

"Sure," Len said somewhere.

Rin lead the way to somewhere vague, but in truth she was losing Len in the crowd.

 _Does it look like I want to get along with anyone? Just leave me alone!_

She stumbled out into the backyard garden and somehow found the way to her nook before collapsing on the ground in tears.

* * *

 **A/N: Thanks for reading! I originally wrote this chapter much longer with the entire first verse rather than just the first line, but this is already like over 1,000 words, so I'll just keep it this short. Not that I've written any other chapters for now, but still.**

 **Reviews are always appreciated!**


	2. Chapter 2

**A/N: 3 reviews! And in just 2 days! That's surprising. Thank you to all of you!**

 **Anyway, here are my responses:**

 **ilovevocaloid93: Yes, Rin is technically older than Len, and Miku and Rin aren't related in canon, but it's called FanFICTION for a reason; I'm sure you can find lots of other fanfics or even songs by composers where people take liberty with things like that. But thank you for pointing it out :)**

 **Red-Demon-Angel: Thank you for your kind words! It's okay if you rant, I'm sure everyone does it at one point X3**

 **Azure-Blue-15: Thank you! I'm glad you like it :D**

 **Outfits mentioned are from Adolescence, Deep-Sea Girl and Just Be Friends. (You may see a bit of a theme here XD)**

 **DISCLAIMER: I don't own Vocaloid... but someday...**

* * *

"Rin."

She slowly raised her head dispiritedly at Luka's voice. "What?"

Luka was crouching on the ground next to her in a white sundress and black boots, a flower crown nestled into her loose pink waves. How Luka survived in clothes like that when it was freezing cold outside, Rin didn't know, but she felt a burst of shame that Luka should see her crying in her garden with a few dozen half-dead frosted roses around her in a white dress with ruffles; next to her, Rin felt almost childish. Considering Miku's wardrobe, however, she was actually rather lucky that it was Luka with her rather than her sister, who had dressed up for that day in a fluffy black dress that trailed down to the right and black ballet shoes. Why couldn't she be like them, all cool and calm and elegant composure? _They_ wouldn't have collapsed in their backyard in tears just because someone they loved for 7+ years evidently didn't feel the same way about them. Okay, maybe that _was_ a valid reason to hide in the backyard, but still, they wouldn't have done that. They would have _done_ something about it.

"Everyone's looking for you," Luka said. "Your sister's warding their questions off, but still, they'll remember it's your party that's being thrown sooner or later."

Rin couldn't muster the energy to sit up, so she just stayed slumped on the floor in a kind of apathetic defeat. "Ugh. Can't they just forget me?"

"No, they can't." Luka's look softened slightly. "Look, I know it's hard for you that Len likes someone else, but it's still your birthday, and you of all people shouldn't forget that."

Rin's head jerked up in panic. " _Did you tell Miku?_ "

"No, I didn't. Yeez, calm down."

"Ah. Good." There were just some things one would rather not tell one's elder sister, after all, or they would have them hanging over their heads for the rest of their lives.

"Well, when are you coming?" Luka asked. "Later," Rin replied, sighing as she wiped the tears off her face.

"Okay." Luka nodded, pressing a hand onto Rin's head. "Take it easy."

"I'll try. Thank you, Luka."

* * *

Easier said than done, Rin couldn't help thinking.

For about the rest of the party, Neru and Len had held hands, exchanged meaningful looks, et cetera, and it had taken all of Rin's will to not grit her teeth and storm out of the room like a drama queen. Of all the things Rin was, a diva was not one of them, and she generally left those kind of things to her sister, though she couldn't deny that she'd dodged interacting directly with Len as much as she possibly could.

Rin lifted her head from the window, absorbed in thoughts. Why, of all people, Neru? She just couldn't understand and couldn't help being unreasonable. Why wasn't Len just as likely to go out with her as he was with Neru?

Didn't everything come from small beginnings?

On impulse, Rin picked up her phone and called Len.

"Hey, Len, a beginning is always trivial, right?" she said when he picked up.

"Uh, yeah, sure..." he replied. "Listen-"

"Thanks, just wondering," Rin said curtly and hung up.

* * *

 **A/N: Why Rin**

 **Why you so random**

 **Anyway, thanks for reading. Reviews are always appreciated!**


	3. Chapter 3

**A/N: A review? Who could it be?**

 ** **Ah, it's you again? Thank you,** Azure-Blue-15!**

 **Anyway, I'm sorry for doing this to Rin :P But you'll find out why Len is doing this one day, I'm sure, cause I'm probably going to create a companion fic for this someday** **, telling Len's version of the story. So don't hate him yet X3**

 **Also, this chapter is longer, so hang in there! I'll try to upload faster, but I have a weeklong trip coming up, so I might not be able to upload new chapters for the duration of it.**

 **Outfits mentioned are actual legit costumes in Project Diva.**

 **DISCLAIMER: I don't own Vocaloid... but someday...**

* * *

Rin couldn't help but notice Len was practically chirping the next day; as she watched from the window, Len skipped across the street in arcs so wide they were almost grand jetés, feet set delicately en pointe and high-pitched notes floating from the pavement. Neru was walking more calmly behind him with a half-embarrassed, half-amused face as he raised his arms above his head and- horror of all horrors- did a perfectly feminine pirouette. Rin shook her head. A pirouette, of all things. Would the joys never end?

Len danced over to Rin's house and rung the doorbell; At this point, she was surprised he wasn't in ballet shoes. When she answered the door, Len sang, "We can watch the fireworks today, Rin! It's the last day of the year! You can stay up till midnight, right? We can go anywhere we want! Where do you want to go?"

Rin smiled; Len's enthusiasm was contagious. She stopped smiling at the last two sentences, however, all too aware that the "we" Len was talking about was no longer "we" as it had been for the last 12 years. Her gaze drifted to Neru in the distance. Where did it all go wrong? If things were going to change, why couldn't he ask Neru instead?

"Don't ask me where I want to go, I can't give you an answer," she murmured quietly, only half to herself.

"What?" Len asked. His playful expression turned more somber when he noticed Rin's depressed eyes. "Rin, is everything okay?"

 _No. Everything is not okay, nor will it be okay ever again._

 _I don't want to be the third wheel._

"Rin, I-"

"Argh, wait uupppp!" Neru could be heard shouting before she skidded to a stop beside them. "So, have we decided where to go yet? We need to keep occupied for..." Neru looked at her watch. "... 13 hours, but not too occupied or we'll feel too tired to watch the fireworks!"

"I don't know where to go," Rin said with a smile she did not feel. "Why don't you go by yourselves? I need to help Miku with her party anyway."

* * *

Except, of course, she didn't; In fact, if she tried to help, she would probably end up getting in the way. No, of course not. She'd only wished to be alone and far, far away from wherever Len and Neru might be, because staying holed up in her room was only about, oh, infinity times better than hardcore third wheeling?

Her thoughts turned to the annual end-of-year party Miku always planned ever since she was 11. In a few hours' time, guests would start arriving, and there would be games and snacks and general insanity until the last five minutes before midnight, during which Miku would get everyone calmed down and fidgety and anxious and anticipating as everyone wondered, _Is it next year yet?_ Then all of a sudden it _would_ be and Miku would scream, "HAPPY NEW YEAR, GUYS! ANOTHER YEAR ON THE COUNTER!" and everyone would whoop and shout and hug each other, then the guests would go home with wild, messy hair and party hats and lopsided grins on their faces at the memories freshly made, exhilaratingly, inexplicably happy.

Miku had always been a gracious host, after all, and her parties were always a blast, even though she did them only rarely and she stressed over every single detail. Not to mention she had a spectacular wardrobe, and some of her outfits were even handmade specifically for herself. Was it any wonder Miku was popular?

If Rin were more like her sister, would Len like her more?

Rin's eyes darkened at the thought of Len and she glanced out of the window to see that the sun was setting. Good. That gave her plenty of time to be gone before he returned to his house. It was only across the street, after all, and Rin didn't want to be there when [insert sarcasm here] the happy couple returned from their day-long excursion, did she?

No, of course not.

She reached into her closet and pulled out whatever caught her fancy, which turned out to be a white full-body hoodie with alpaca ears. An "alparka", she'd liked to call it. Ignoring the fact that Len had, once again, a matching outfit for it, she pulled the hood over her head and stuffed her legs into tights, a white version of her normal leg warmers, and cream flats, setting out just as the sun came down.

* * *

 **Thanks for reading. As always, reviews are appreciated!**


	4. Chapter 4

**A/N: ARRGGHH! Sorry for being away for so long! It's just that unlike most people, I don't have a computer or a phone I can call my own, so most of the previous month was spent lazing around because writing is so much slower than typing and I tired of it quickly. Also, it was kind of an effort to phrase things properly and make the chapter long enough, as I promised(see below), so there's that.**

 **Anyway, here's my A/N before the insane gap since my last chapter:**

 **YAY! 3 reviews when I was away! You people are awesome! Thank you :')** **Replies:**

 **Azure-Blue-15: So... so kind-! *cri :D* Okay! I'll try to make chapters longer, like maybe 1,000+ words this time? And of course a 3rd wheel is worse than never seeing him again, since then you have to endure the happy couple and pretend to be happy for them and etc :P**

 **Red-Demon-Angel: Haha, it's fine XD I do it all the time. Thank you for your patience, btw. =v= Also, that's a bit odd because I'm trying to keep the angst kind of light here, so I guess I'll either have to lighten it even more or make it more evident, because it can't be good if I'm making the plot differentiate in any way than what I intend it to be... (-_-;)**

 **Neame kke: Yes, you're right! Len isn't trying to hurt Rin on purpose.. but that's all I'll say about it for now. Neru isn't doing anything (bad) to the outfit, so don't worry about that either. And thank you XD Like I said (or wrote) earlier, the next chapters will be longer, so hopefully it can counter that.**

 **Also, since there's such good reception for a companion fiction for Len, I'll publish one! But you'll have to wait for a while before it's published, because spoilers. I might not even publish it until I finish this one.**

 **Oliver and Yuki are about 3/5 years younger than their official ages, 7 and 8 respectively.**

 **Outfits mentioned are the official outfits for the Vocaloids mentioned.**

 **DISCLAIMER: I don't own Vocaloid... but someday...**

* * *

Rin wasn't really planning to go anywhere; as she wandered in the streets aimlessly, her eyes were focused on the night sky, with only the luminescent moon and her fancy guiding her way as they wished. She walked like that for about an hour before she noticed her legs were aching and began to look for somewhere to sit, when she realized she was lost.

Frankly put, _shit_.

She looked back up at the stars and stuck her tongue out at them. _Delude me, why don't you_ , she thought cynically.

Glancing down the street where she was, she noticed a small but seemingly cozy sushi restaurant tucked amidst the rest of the shops. It seemed approachable enough, so Rin crossed the road.

Just before she entered, however, a small group of two women and two children exited. Rin withdrew her hand from where she'd reached out for the door and listened, curious.

"Oli, Oli, Oli!" One of them yelled, bouncing around the other child. She was small- Rin guessed 6 or 7 years old- and had on a red-and-white school-style dress, knee-length socks, and red school shoes. Her hair was tied into two pigtails. Oli seemed about a year older, with a sailor cap and coat, and shorts not unlike Rin's. He wore a bandage on his left eye.

"We're going to go to the Yōnenjidai park!" The girl continued. Rin perked up. Wasn't that the park she and Len used to go to?

The boy- Oli- seemed to brighten at this as well. "Oh, really? We haven't been there in a while."

Rin could follow them, she realized. She might as well; she was lost anyway, and she knew the way back home from the park. She pulled the alparka hood more securely over her head and wandered behind the group.

As she meandered slowly behind them, Rin let her mind wander. How curious it was that those two children seemed so similar to the way she and Len used to be. Rin and Len used to live on opposite sides of the city, but their parents had met at the childcare centre. Since then, both parents and offspring had been firm friends and met often despite how far they lived, most often at that park. Rin wasn't sure what might have happened when they grew up if things just stayed that way, but she _was_ pretty sure the day she learned Len's family would move across the street had been one of her happiest.

In other words, it just seemed like Len had been in her life since the beginning, even though he wasn't, even though he came pretty close. And wasn't it a trope for two childhood friends to fall in love with each other?

Hey, couldn't she even dream?

Oh, yeah, but ugh, Neru.

Realizing they had reached the park, Rin slumped onto the nearest park bench with relief; her legs were killing her. Idly, she watched the girl and Oli. The girl had, apparently, scraped her knee; Oli was comforting her. Rin could hear a little of their conversation.

"... it hurts... bandage..."

"...fine... Yuki... the princess... your knight, remember?..."

Even the promise of being a knight and princess had once been Rin and Len's. Argh, but those two were just them all over again.

And no, Rin didn't feel like thinking about _that_. Not now, at least.

Or ever.

Was it really that bad to be nostalgic, though? Because nostalgia was stabbing through Rin, and she wanted nothing more than to shelter those two-Oli and Yuki, it seemed- from growing up. Growing up just complicated things-and far, far too much.

Rin threw her back against the bench in frustration. If only she could return to that time. If only.

She stared out the night again, where the Milky Way glinted in the heavens, as gibberish groggily ran through her mind. I _may have lost my way because of you_ , she thought sleepily, _but doesn't that just mean you're beautiful?_ Though she had been thinking of the night, Len came to mind. Argh, but would she _never_ be free of thoughts of him?

That was one of her last thoughts before she fell asleep right there on the park bench.

* * *

"Shit!"

Rin leapt up and stretched as fireworks went off above her head. Midnight, obviously. That meant that she had been missing for roughly 5 and a half hours, 4 of which had been spent sleeping. Boy would she ever be in the doghouse for _that_ one.

Oh, but who cared? Was she anything other than in people's way half of the time? Rin swung her legs and stood up. Enough of that angsty shtick, Rin. C'mon.

With a final sigh, Rin stuffed her hands in her pockets and strolled home.

* * *

 **A/N: Centre can also be called center. Hey, chill. It's the British spelling.**

 **If no one cares enough to Google it, Yōnenjidai is Japanese for Childhood.**

 **As always, pls review (●ω●)**


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